Abstract

Tolerance measure is an important part of engineering, however, to date the system ofapplying this important technology has been left to the assessment of the engineer usingappropriate guidelines. This work offers a major departure from the trial and error or randomnumber generation techniques that have been used previously by using a knowledge-basedsystem to ensure the intelligent optimisation within the manufacturing system. A system tooptimise manufacturing tolerance allocation to a part known as Knowledge-based AutomaticTolerance Analysis (KATA) has been developed. KATA is a knowledge-based system shellbuilt within AutoCAD. It has the ability for geometry creation in CAD and the capability tooptimise the tolerance heuristically as an expert system. Besides the worst-case tolerancingequation to optimise the tolerance allocation, KATA's algorithm is supported by actualproduction information such as machine capability, types of cutting tools, materials, processcapabilities etc. KATA's prototype is currently able to analyse a cylindrical shape workpieceand a simple prismatic part. Analyses of tolerance include dimensional tolerance andgeometrical tolerance. KATA is also able to do angular cuts such as tapers and chamfers. Theinvestigation has also led to the significant development of the single tolerance referencetechnique. This method departs from the common practice of multiple tolerance referencingtechnique to optimise tolerance allocation. Utilisation of this new technique has eradicatedthe error of tolerance stackup. The retests have been undertaken, two of which are cylindricalparts meant to test dimensional tolerance and an angular cut. The third is a simple prismaticpart to experiment with the geometrical tolerance analysis.The ability to optimise tolerance allocation is based on real production data and not imaginaryor random number generation and has improved the accuracy of the expected result aftermanufacturing. Any failure caused by machining parameters is cautioned at an early stagebefore an actual production run has commenced. Thus, the manufacturer is assured that theproduct manufactured will be within the required tolerance limits. Being the central databasefor all production capability information enables KATA to opt for several approaches andtechniques of processing. Hence, giving the user flexibility of selecting the process plan bestsuited for any required situation.